When my agent mentioned this production of Saturday Night I was mad keen, because I know it from drama school and often sing one of the songs as an audition piece. So even before hearing anything about the production, I said I would do it if only so I could sing that song! And my instincts were right, because I'm having an absolutely brilliant time doing it.

A lot of people view the show as 'singable Sondheim'. He was only 23 when he wrote it, and was working a lot with Richard Rodgers, so it has a real Rodgers and Hammerstein influence and there's a bit of Gershwin in there too. So even people who don't particularly know or love Sondheim can enjoy this show. It also has a real contemporary resonance as it's set in Brooklyn just before the Wall Street crash and is about a man who gambles his money away on the stock market. He then meets and falls in love with my character Helen, who helps get him back on the straight and narrow.

The perceived wisdom is that it's not one of Sondheim's best works, partially because he was so young when he wrote it, and also because by the end it gets quite cheesy. But I think the writing's really good and there's some great wordplay in there and a real insight into what was going on very early in his life. It's not Merrily We Roll Along or Sunday in the Park with George, it’s completely the opposite and I think that’s what makes it lovely. And considering he was writing it in the 1950s it's very ahead of it's time.

This is actually something of a UK premiere, because it includes two songs - "Delighted I'm Sure" and "Montana Chem" - that weren't in the 1997 Bridewell Theatre production. Sondheim wrote them especially for the 1999 US premiere run. It's also the first time the show has been in the West End, which is great because so often when you're doing Sondheim you have so many previous productions to match up to, but I don't think many people will have preconceptions of Saturday Night.

I never regret not winning the role of Maria – I wasn't really right for it. I've had a great time since then, doing all kinds of projects including Gypsy, Wizard of Oz, South Pacific, Night of a Thousand Voices at the Albert Hall and A Spoonful of Stiles and Drewe in the West End. Obviously the casting show format has divided opinion but I think what's positive is that they're usually won by professionals, people who give it absolutely 110%. But inevitably they create a large number of additional performers to the 100s already leaving drama schools each year, and sadly there just isn't enough work to go round. But at least they keep finding variety – for Maria they got a soprano, for Joseph they got a boy and for I'd Do Anything they got a belter, so it's not like they're always picking the same types. And as long as they keep feeding new audiences into our industry, I don't see the problem.


Saturday Night opened last night (25 March 2009) at the Arts Theatre, where it continues until 11 April 2009.